Conveyor sorter with a diverter gate

Parts in this circuit

Wiring, pin by pin

Red = 5 V, orange = 3.3 V, black = GND, other colours = signals. “Pin” is the position on the 40-pin header; the GPIO number is what the code uses. Power the Pi from a 5.1 V supply and wire with the power off.

Python code (gpiozero)

from gpiozero import Motor, Button, AngularServo
from time import sleep

belt = Motor(5, 6, enable=12)
low = Button(4)               # beam 3 cm above the belt
high = Button(22)             # beam 8 cm above the belt
gate = AngularServo(13)       # -45 degrees = bin A, +45 degrees = bin B

short_count = 0
tall_count = 0

belt.forward(0.6)             # run the belt at 60 % speed
gate.angle = 0
print("Belt running. Use the buttons under the board to send parts.")

while True:
    low.wait_for_press()      # a part has arrived
    sleep(0.05)               # let both beams settle
    if high.is_pressed:
        tall_count += 1
        gate.angle = 45
        print("TALL part -> bin B   (tall:", tall_count, ")")
    else:
        short_count += 1
        gate.angle = -45
        print("SHORT part -> bin A  (short:", short_count, ")")
    low.wait_for_release()    # wait until the part has gone

How the code works

• The belt motor runs the whole time at 60 % speed. In a real machine you would stop it in an emergency, as in project 20.
• The low beam tells us a part has arrived. After a short wait we check the high beam. If it is also broken, the part is tall.
• The servo gate turns to the correct side before the part reaches it. A real machine needs a delay that matches the belt speed and the distance to the gate.
• wait_for_release() makes sure one part is counted only once, even though it takes time to pass.

Parts to buy

The links open a search on each store, so you see what is in stock today. Check the model, voltage and price before you order.